The present invention relates, generally, to the field of sail and mast assemblies for sailing vessels. More specifically, the invention relates to a sail and mast assembly of the type commonly found on sailboards and small sail boats, in which the sail area is easily adjustable to suit various wind conditions and sailing skills.
The popularity of sail-driven surf boards, frequently termed "sailboards," has been increasing in recent years. Briefly described, a sailboard comprises a buoyant elongated platform or board having a tapered "bow", on which a mast carrying a sail is mounted. The mast is mounted to the board by means of a universal joint, allowing the mast to be turned and twisted, by means of a laterally-extending boom, to adjust the attitude of the sail with respect to the wind, thereby controlling the speed and course of the board.
The sail on sailboards usually has a fixed, non-adjustable area. The area of the typical sailboard sail (i.e., approximately 60 to 64 square feet) reflects a compromise between a larger sail suitable for light wind conditions (a "light air" sail) and a smaller one adapted for heavier wind conditions (a "heavy air" sail). Thus, the typical sail is an attempt to optimize performance in average wind conditions, and is, therefore, not suited for optimal performance in light or heavy wind conditions.
Enthusiasts who seek optimum performance and handling at all times therefore resort to the use of different size sails for differing wind conditions. Aside from the expense involved in purchasing two or three different sails, there is the inconvenience of changing sails as wind conditions change, which necessitates the beaching of the board.
It has also been found that those who are inexperienced in the use of a sailboard find it easier to learn the necessary skills with a smaller sail, such as a heavy air sail. Thus, if a sailboard is to be used by both a novice and an experienced user, an additional sail must be purchased.
The use of a separate heavy air sail has a further disadvantage, in that the leading edge ("luff") of the sail starts two or three feet from the top of the mast. This results in compromised sail handling, due to the carrying of unnecessary weight aloft.
It has been proposed to adjust the area of a fixed sail by removing sections of the sail from its trailing edge, or leech. While this procedure allows the use of a fixed-length mast, a disadvantage exists in the rather drastic change in sail shape which results. Specifically, the leech is moved closer to the line of maximum sail curvature (the "draft line"), and this can degrade the optimal sail shape, in which the draft line is located approximately one-third to one-half of the distance from the luff to the leech.
Thus, there exists a long-felt, but unsatisfied need for a sail and mast assembly, for sailboards and the like, which allows adjustment of the total sail area without degrading the aerodynamic characteristics of the sail, or its handling qualities. Moreover, it would be advantageous for such an assembly to provide for ease and convenience in adjusting the sail area, while being capable of incorporation into existing sailboard designs.